When sowing crops such as maize, sunflowers and soya beans it is desirable to plant, in each row, single seeds at a predetermined distance from each other. This requires a device for singling out single seeds from a hopper containing many seeds. An example of such a seed distributing device is disclosed in EP-0 216 057 B1. The distributed seeds are fed by means of an excess pressure in the hopper through a tube to a seed knife, which creates a furrow in the ground into which the seeds are dropped.
In many practical applications, a seed knife is not enough to provide optimal conditions for the seed.
A seeder known in the art, which is marketed by Amazonen-Werke H. Dreyer GmbH under the name Amazone EDX and which has a seed distributing device according to EP-0 216 057 B1 mentioned above, uses a pair of sowing discs, which operate at a forwardly oriented acute angle so as to make a furrow, and where the seed knife is located partly between the sowing discs. Arranged after the seed knife is a press wheel, whose function is to apply pressure on the seed to ensure satisfactory contact between the seed and the soil, and a pair of wheels, which operate at a rearwardly oriented acute angle relative to each other to cover the seed with soil.
In seeders where the seeds are fed by means of an excess air pressure the seeds usually travel at a relatively high speed as compared with seeders where the seeds are singled out using a vacuum technique and are then allowed to drop by gravity through a seed discharging tube. Speeds of up to 15 m/s are not uncommon. The seed knife ensures here that the seed lands in the intended spot in the furrow and does not bounce off before the succeeding press wheel is able to press it down.
However, the seed knife is a wearing part, which needs to be replaced a number of times during the life of the seeder. Furthermore, when using a seed knife there is a risk that plant residues get stuck, eventually causing malfunctioning. There is also a risk that the seed knife is damaged by obstacles, such as stones, in the ground, thus causing operating disturbances.
There is therefore a need to provide a seeder that solves the above problems while maintaining its precision.